Uses DEVELOPER_DIR instead of hard-coded path to Xcode

[lyricsboy]

Uses a shell script as a post-build action in the schemes to post-process the module maps.

This is a little bit of a hack, but it seems to work fine. What do you think, @soffes ?

The goal is to make this work regardless of where Xcode is installed.

[soffes]

Interesting. How are you setting DEVELOPER_DIR?

[lyricsboy]

It's set by the build process automatically. The typical value is /Applications/Xcode.app/Contents/Developer

[lyricsboy]

Don't merge this just yet; it worked locally when I built using Carthage but is failing on CI for some reason.

[lyricsboy]

OK, I added some magic quotes around shell variables in the script, and that seems to have made my CI environment happy (it uses spaces in the derived data folder path).

This works for me now, but there are still a couple of caveats:

• it doesn't make the built product any more portable. Using a CommonCrypto.framework built with Xcode at a different path than the machine using it to build the app will still fail (e.g. build the framework, zip it up using carthage_cache and distribute it to an environment with a different path to Xcode).
• the better fix would be to somehow use relative paths to the system include, or variable expansion in the module map in a supported way. I'm not sure that either of these are possible with the current module map design.

[soffes]

@lyricsboy thanks for checking all of those variations. Do you have any ideas to solve this?

[lyricsboy]

None yet. I'm not familiar enough with module maps to say for certain if there's a better supported way. I see these changes as a marginal functional improvement, in that they support building with a non-traditional Xcode path.

If you want to merge them, I think it would be good for me to document this fanciness in the README first.

[soffes]

I'll probably keep it simple to avoid unexpected behavior of mixing like you discovered. Thanks for your work on this.

I don't know what I'm doing either :) Just figured out enough to get this to work. It's a real shame this is necessary in the first place.

[iandundas]

This was super useful & solved our issue, thanks @lyricsboy.

If anyone needs it the pull request branch is available here, i.e. github "iandundas/CommonCrypto" "developer_dir" in Carthage. I'll leave it there forever.

(I couldn't work out how to point Carthage directly to this PR, so I forked it.)

[soffes]

Fixed in e3d71cd